Sigma 17-70mm f/2.8-4 DC Macro OS Lens Review

The Sigma 17-70mm f/2.8-4 DC Macro OS Lens features a great general purpose focal length range, short minimum focus distance,
HSM autofocus and OS (optical stabilization) in a well-built and very affordable lens.
Its image quality is not all I hoped for.

The 17-70mm focal length range very comfortably covers the recommended general purpose lens
focal length range for the APS-C sensor format DSLRs it is compatible with.
This focal length range delivers that same angle of view that a 27.2-112mm lens on a full frame DSLR would deliver,
but again, this APS-C-only lens is not compatible with the larger format SLRs.
Here is an example of what this focal length range looks like.

Many general purpose lenses have a maximum focal length of 50 or 55mm.
The welcomed 20mm of additional focal length available on this lens is obvious when comparing the last two samples above.

It is hard to find anything wrong with the 17-70mm focal length range - it works great for a wide range of subjects and activities.
I think I could spend weeks creating the list of subjects this focal length range could adequately capture,
but family events, vacation memories and portraits are sure to be captured with this lens mounted.

In addition to having an extended FL range over many general purpose lenses including many of the kit lenses,
the Sigma 17-70mm f/2.8-4 DC Macro OS Lens also has a wider aperture than many of these lenses.
The 17-70's max aperture is not, however, fixed over the focal length range.
This means that wide open exposures will change as the focal length is increased.
Below is a chart of max aperture step downs of some similar lenses.

Aside from the fixed f/2.8 max aperture lenses, the Sigma 17-70mm f/2.8-4 DC Macro OS Lens shines in this comparison.
It offers about a stop of advantage (2x as much light) at 70mm over the others.
However, many of these competing lenses have a longer focal length available - as much as 270mm.
So once again, there is a tradeoff - the perfect lens does not yet exist.

The advantages of wider apertures include the ability to use a faster shutter speed - which will help stop action in low light and will allow handholding in even lower light.
Wider apertures also deliver shallower DOF (Depth of Field) for a more-blurred background.
F/2.8 is the widest aperture currently available in a zoom lens and f/4 is still a reasonably wide max aperture.

It is easier to create a blurred background with longer focal length lenses (they magnify the out of focus background),
but I wanted to take a closer look at the background blur possible at 17mm.
Here is a 17mm comparison.

This comparison was shot handheld - using a Canon EOS 60D (utilizing the vari-angle LCD) resting on my hand which was on the ground.
The shutter speeds ranged from 1/20 to .8 seconds.
These slow semi-handheld shutter speeds were made possible by OS.

If your subject is not moving, the Sigma 17-70's 4-stop-rated OS (Optical Stabilization) will be a great help in achieving sharp handheld shots in low light,
in the wind, on unstable footing, on a boat ... and in other situations where holding a camera steady is difficult and a tripod in not being used.

At 17mm, I am getting a good rate of sharp images from the Sigma 17-70mm f/2.8-4 DC Macro OS Lens at 1/4 sec exposures for a net 3-stops of assistance from OS.
I have some sharp shots taken at shutter speeds as long as .6 seconds, but the keeper rate is very, very low at this exposure duration.
At 70mm, 1/10 is about my shutter speed limit for sharp images.
This is just under 4-stops of assistance from OS.

Quite often, lenses with longer focal length ranges have lesser image quality than shorter focal length range lenses.
This rule does not always hold true - especially if there is a large price disparity between then lenses, but in this case,
I'm sorry to report disappointment with the Sigma 17-70 OS' image quality.
The 17-70mm range is not dramatically longer than the Sigma 17-50's, but the image quality is decidedly worse.

I wrote much of this review on the heels of writing the
Sigma 17-50mm f/2.8 EX DC OS HSM Lens Review.
Though these lenses have some significant differences, they are nearly identical in many aspects including appearance and build.
So similar that, on two separate occasions, I grabbed the wrong lens.
Unfortunately, I had the 17-70 in my case instead of the optically-superior 17-50.

One of those times was when I was shooting the wild mustard field shown in the focal length comparison above.
This was a scene I wanted to capture in high quality, but loaded the 17-70 in my Pelican 1510 Case
and didn't have time to go back for the other lens.
So, I simply made the most of the situation.
My results, even at f/11, were softer than I had hoped for.

If you simply look at the ISO 12233 chart results from the Sigma 17-70mm f/2.8-4 DC Macro OS Lens, you would think that it is a reasonable, though not stellar, performer.
Except at 70mm where the image quality falls apart even on the ISO chart (yes, the focal length range advantage has just partially evaporated).
The outdoor comparison results, shot at longer distances, were less exciting.
Generally, an aperture of at least one stop narrower than wide open is needed for decent center of the frame sharpness.
The need for a 1-stop narrower aperture is not unusual, but the Sigma 17-70's corner image quality lags well behind the center of the frame image quality.
And in this case, the corners I'm referring to extend well into the frame.
The image quality from this lens is also complicated somewhat by some side-to-side unevenness around the image circle - which varies from focal length to focal length.

I included the Sigma 17-70 OS in a set of tests with some f/2.8 lenses and I'll share those results here.
The first comparison test results are from the absolute top left corner of the frame out of a
Canon EOS 60D using the Standard Picture Style and a sharpness setting of "1" (very low).
Lenses were set to approximately 28mm.

The same tripod-mounted camera position was used, but corner framing is not identical
due to lens focal length marking discrepancies and my guess at the focal length setting on lenses not having 28mm marked.
These 28mm results are generally indicative of the performance of these lenses over their entire focal length range.
To show the desired results, a mouse click on the aperture labels is required.

Note that, to reduce page load time (especially for mobile users), this comparison is being hosted on a separate page.
Click on the image below to open this comparison in a new window while reading the discussion on this page.
Use Alt-Tab to toggle back and forth.

The Sigma 17-70mm f/2.8-4 DC Macro OS Lens shows poor corner performance even stopped down to f/8 or f/11.
The disappointing corner performance can at least in part be attributed to a curved plane of sharp focus.
I know, "curved plane" is an oxymoron, but hopefully you get the picture.
If I'm focusing 50' or 50m away, having my feet in focus is probably not as important to me as having the line of trees in focus.

Most lenses perform best in the center of the frame and the 17-70 does perform better here.
Again click on the image below to see the comparison.

The above comparison images were shots with the Canon EOS Rebel T3i/600D
using the Standard Picture Style and a sharpness setting of "1" (very low).
I expect that you will minimally want to use f/5.6 for decent center-of-the-frame results at 50-70mm.

The Sigma 17-70mm f/2.8-4 DC Macro OS Lens controls vignetting quite well.
With a wide open aperture, expect to see about 1.5 stops of peripheral shading in the corners.
Stopping down to f/5.6 removes much of the corner shading and by f/8, only about .5 stops of shading remains - even less at 70mm.
A normal thickness circular polarizer filter
will add a small amount of mechanical vignetting at 17mm - even at f/11.

Some chromatic aberration is noticeable in the corners at the wider end of the focal length range.
To generalize, CA is worst at 17mm and slowly improves through the balance of the focal length range with slightly more visible again at 70mm.
The amount of CA exhibited is not unusual for a lens in this class.

With regard to flare, the Sigma 17-70mm f/2.8-4 DC Macro OS Lens performs quite well also.
Varying amounts of flare show over the focal length and aperture ranges, but overall, it is a decent performer in this regard.
Bokeh (background blur quality) generated by the 7-blade aperture appears to be only fair and a bit edgy - I am seeing a bright edge on out of focus details.

Most zoom lenses with focal length range of 17-70 or greater will show distortion and the Sigma 17-70 is no exception.
At 17mm, the Sigma 17-70 exhibits an average, noticeable bulge-in-the-middle barrel distortion.
This distortion quickly transitions to mild pincushion distortion by 24mm and proceeds to moderate pincushion distortion by 50mm.

Overall, the Sigma 17-70 OS' image quality is mediocre.

The 17-70 OS incorporates Sigma's (Hypersonic Motor) for moderately fast autofocusing.
Though reasonably quietly, the 17-70 generates some gear noise during AF.
AF accuracy has proven to be fine with my use of this lens.

Focusing is internal - the front element does not extend or rotate.
Expect a relatively small amount of focus breathing from this lens - the subject/framing changes size a small amount when focusing.

FTM (Full Time Manual) focusing is not featured in this HSM AF implementation - the focus ring turns during AF.
Keep your hands off of the focus ring during AF to avoid gear damage.
A printed-on-the-MF-ring focus distance scale is provided - and this reveals the lack of FTM.

The focus ring is nicely sized and in the location I prefer for a lens most typically used in AF mode - as the front-most ring.
The Sigma 17-70 focuses smoothly, but with a relatively short 54° rotation and low rotation resistance, precise focusing is somewhat touchy.

The table below reviews a large number of general purpose lenses' minimum focus distances and maximum magnifications.

Sigma includes "Macro" in the official name of this lens.
A "macro zoom" is usually an oxymoron in my mind, but this one comes closer to what I would consider a real macro lens (a 1:1 reproduction ratio)
than nearly all other Canon or Nikon mount zoom lenses.
The Sigma 17-70mm f/2.8-4 DC Macro OS Lens' .37x maximum magnification value is best-in-class.
The minimum focus distance reproduction ratios are printed on the extending portion of the lens barrel (shown below).

Like most Sigma lenses, the Sigma 17-70 OS has very good build quality.
I have not been a big fan of Sigma's matte finish - especially because it readily shows fingerprints and dust.
The 17-70's hood and ring edges retain this finish.
Fortunately, most of the lens barrel is rubber zoom ring - and the mount area has a nicer, smooth finish.

The focus and zoom rings are very smooth with no play.
The zoom ring has an ideal amount of resistance while the focus ring is slightly too easy to rotate.

Like all other zoom lenses in its class, the Sigma 17-70mm f/2.8-4 DC Macro OS Lens extends when zoomed to its longest focal length.
The Sigma 17-70 has a two-piece extension that exhibits very little play even when fully extended.

My purchased-retail copy of this lens does not exhibit gravity-zooming behavior, but a lock switch is provided to assure the lens stays retracted at 17mm.
The other two switches - AF/M and OS On/Off are noticeably raised from the lens barrel.
These switches are located close enough to the lens mount that they are not uncomfortable during use, but they are easy to find with your left thumb.

The relatively small lens hood is large enough to help keep fingers and other objects from touching the front element.
The Sigma center-and-side-pinch lens cap is very nice and is easy to install or remove with the hood in place.

The Sigma 17-70 OS is in the middle of its class in the size and weight categories.
I find a lens with this size and weight to be easy to take with you, comfortable to use and to have enough mass to be stable.

The medium 72mm filter size is quite common - making the sharing of certain filters easy.

The same lenses are shown below in their fully extended states with their lens hoods in place.

You can create your own comparisons using the
Sigma 17-70 OS Image Comparison.
Click on the image below for an additional copmarison (opens in new window to save your place in this review).

The Sigma 17-70mm f/2.8-4 DC Macro OS Lens is available in Canon (reviewed), Nikon, Pentax, Sony/Minolta and Sigma mounts.
My standard disclaimer: There are some potential issues with third party lenses.
Since Sigma reverse engineers (vs. licenses) manufacturer AF routines,
there is always the possibility that a DSLR body might not support a (likely older) third party lens.
Sometimes a lens can be made compatible by the manufacturer, sometimes not.
There is also the risk of a problem that results in the lens and body manufacturers directing blame at each other.
Sigma USA's 4-year warranty is far superior to Canon's standard 1 year warranty (Sigma's international warranty is also 1 year).

While the Sigma 17-70mm f/2.8-4 DC Macro OS Lens has many things going for it, including good build quality, a nice focal length range, a reasonably wide aperture and nice price tag,
the image quality from this lens is not all I'd hoped it to be.
My goal is always to give you the information you need to make your own buying decision, but I highly advise that you check out the
Canon EF-S 15-85m f/3.5-5.6 IS USM Lens review if you are looking for a general purpose zoom lens
with a modestly longer than 18-55mm or so focal length range.

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